The present invention relates generally to agents for promoting oral health in domestic animals such as dogs and cats. More particularly, the invention relates to products such as rawhide to be chewed by animals and including agents that promote oral health.
As further background, dental calculus, commonly known as tartar, is recognized as a recurring calcified deposit that occurs on the surfaces of the teeth of companion animals, particularly domestic dogs and cats. Dental calculus forms as a sequential process that begins with the formation of dental plaque, a biofilm consisting of about 70-75% oral microorganisms with variable amounts of food debris and microbial remnants. Beginning with a clean tooth surface, within seconds following exposure to saliva a thin organic film (dental pellicle) forms on the tooth surface. Within minutes, oral microorganisms colonize the pellicle coating and, utilizing food particles and salivary components of the host, rapidly grow to form a visible deposit (dental plaque) on the tooth surface within a few hours. Within 24 hours some microbial members of the dental plaque die and their cellular remnants serve as foci for calcification. Because saliva is supersaturated with regard to calcium, the presence of such foci serve to initiate the calcification process in the deeper layers of dental plaque. Thus, within 48-72 hours calcified dental plaque (or dental calculus) can be readily detected microscopically in plaque removed from the tooth surface. This process continues with the progressive increase in the extent of the calcified deposit such that it is typically quite visible to the naked eye within 7-10 days and is readily apparent within 3-4 weeks.
The chemical composition of the calcified deposits (calculus) is related to the pH and composition of the saliva of the host. In dogs and cats the saliva has an alkaline pH and a high concentration of carbonate with very little phosphate. As a result, the composition of calculus in companion animals is predominantly calcium carbonate.
Inflammation (gingivitis) of the soft tissues supporting the teeth (gingivae) is primarily due to the presence of bacterial toxins and related microbial by-products. If this process is allowed to continue the inflammation becomes progressively more severe with invasion of the underlying structures and a subsequent resorption of the bone supporting the teeth resulting in tooth loss (periodontitis). The presence of dental calculus on the tooth surface provides an increased surface area for microbial colonization enhancing the rate on additional calculus formation. Large calcium deposits may serve as a physical irritant to the soft tissues supporting the teeth and enhance the inflammatory response (gingivitis). Thus, the presence of dental calculus is recognized as a secondary factor that may exacerbate the development of gingivitis.
The formation of dental calculus can be prevented by scrupulous oral hygiene involving the complete removal of dental plaque each day by meticulous tooth brushing and the use of dental floss. However, such scrupulous oral hygiene rarely occurs in companion animals, and thus other preventive measures are required.
It is known that the provision of a hard particle diet decreases the amount of plaque accumulation in companion animals, as compared to the feeding of moist or canned regimens. This effect is attributed to the mechanical removal of non-calcified dental plaque during mastication and has resulted in the marketing of a variety of biscuit-type products as snack treats for dogs and cats.
In recent years, specific chemicals that reduce the rate of the formation of dental calculus have been incorporated into commercial products and suggested in the literature. Soluble pyrophosphates have been suggested to act as crystal poisons to reduce the formation of calculus and are included in several current commercial products. Sodium hexametaphosphate is a recognized sequestrant and its incorporation into a variety of products has likewise been shown to reduce the formation of dental calculus in dogs and cats. See, e.g., U.S. Pat. No. 5,296,217 issued Mar. 22, 1994. Sodium tripolyphosphate is presently included in several treat-type products for cats and dogs with claims for reductions in calculus formation, although there are no published clinical data to demonstrate such an effect.
Because many pet foods contain phosphoric acid as a palatant and the presence of phosphoric acid inactivates the aforementioned polyphosphates by converting them to orthophosphate, generally, these compounds may only be used on pet food formulations that do not contain phosphoric acid. It has been reported that the use of malic acid on such formulations containing phosphoric acid results in a decrease in the formation of dental calculus.
In light of this background, there remain needs for products and methods for promoting oral health in domestic companion animals such as cats and dogs. The present invention is addressed to these needs.